1. Field of the Invention
The present invention relates to a developing apparatus and a developing method for use in recording methods based on electrophotographic methods and the like.
2. Description of the Related Art
Known developing apparatuses mounted on image-forming apparatuses such as copiers and printers generally have the configuration in which a blade made of rubber or metal serving as a toner regulating member (also referred to as a developing blade) for regulating the toner coat amount is brought into contact with the surface of a toner-carrying member (also referred to as a developing sleeve).
Toner is provided with positive or negative charge by friction between the developing blade and toner and/or friction between the toner-carrying member and toner. It is a general developing method in which a toner-carrying member containing toner which has been thinly applied thereon by the developing blade allows toner to fly and adhere to an electrostatic latent image on the surface of an electrostatic latent image bearing member opposing the toner-carrying member.
It is recently required that the image-forming apparatus technology is directed to actualize high image quality as well as high image stability for long term use. On the other hand, printing environment has been varied and it is highly required to print in environments varying from a high-temperature, high-humidity environment to a low-temperature, low-humidity environment.
In order to fulfill these requirements, there is a need for a developing apparatus as well as magnetic toner in which toner is uniformly charged and which has high transfer property.
In order to fulfill the above requirements, various trials for improving the developing blade, toner-carrying member or the like have been carried out.
Japanese Patent Application Laid-open No. 2004-4751 proposes the hardness and deformation rate on the surface of a developer carrying member and a developing apparatus in which the ten point mean roughness (Rz) of the surface which contacts the developer carrying member of a developer amount regulating blade is 0.3 to 20 μm. In this patent document, non-magnetic black toner is evaluated on the developing apparatus and it is confirmed that it improves solid image density and prevention of unevenness and streaks. On the other hand, stability in a long term durability test has not been sufficiently evaluated.
Japanese Patent Application Laid-open No. 2007-79118 discloses a trial for improving toner melt adhesion and thin line reproducibility by using a specific toner regulating blade to define the adhesion strength between the toner regulating blade and toner. However, in this document, material of the toner regulating blade or the amount of an external additive(s) is not sufficiently optimized, so that there is room for improvement in terms of low density which particularly occurs after a long term durability test.
On the other hand, toner has also been variously improved. Japanese Patent Application Laid-open No. H06-301236 proposes to produce toner fine powder by kneading a binder resin, a magnetic substance and an optional additive and pulverizing and optionally classifying the mixture to produce toner fine powder, adding an external additive to the toner fine powder followed by surface modification using hot air while it is dispersed in order to simultaneously and instantly carry out fixation of the external additive, coating of the magnetic substance and sphering of toner fine powder.
Japanese Patent Application Laid-open No. 2007-334118 proposes toner for developing an electrostatic image in which a binder resin in toner base particles contains a polyester resin at 80 weight % or more and has a wax/silica weight ratio of 0.5 or more, and when the section of the toner base particles is observed by a transmission electron microscope equipped with elemental analysis ability, (a) silica fine particles having an average primary particle diameter of 15 nm or less are contained in a region 0.5 μm or more inside from the toner base particle surface, and (b) when the section of the toner base particles is stained to distinguish a binder resin portion and a wax portion, 50 number % or more of the silica fine particles of the above (a) are present in the wax portion and a peripheral region within 0.1 μm therefrom.
By applying so-called heat sphering treatment, image quality and image stability for long term use are actually improved. However, there is still room for obtaining a developing apparatus and magnetic toner in which magnetic toner can be charged uniformly in order to allow printing in environments varying from a high-temperature, high-humidity environment to a low-temperature, low-humidity environment and which has a broad transfer region. Moreover, there is also room for improvement in toner haing a low development efficiency without image density non-uniformity which may occur due to possible insufficient matching to the developing apparatus.